Mobile terminal and control method thereof

ABSTRACT

There is provided a mobile terminal capable of being protected against unauthorized use by a third party without using a dedicated key device. A plurality of mobile terminals are previously registered mutually. When unlocked among them, one mobile terminal communicates with another mobile terminal in a communication range of short-range wireless communications, unlocks the above another mobile terminal, and when out of the communication range, locks it again.

INCORPORATION BY REFERENCE

The present application claims priority from Japanese applicationJP2012-117105 filed on May 23, 2012, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

The present invention relates to a mobile terminal and a control methodthereof.

As a background art of this technical field, JP-A-2004-102682 isdisclosed. In its publication, a problem will be described as below.“According to the conventional schemes described above, therefore, theuser of the terminal device needs to make a complex action in order toprevent a third party from making unauthorized use of the terminaldevice. If the user has inadvertently made the password known or lostthe terminal device together with the ID card, then it is impossible toreliably prevent unauthorized use of the terminal device by a thirdparty.”

A method for solving this problem will be described as below. “There isprovided a terminal lock system for verifying that the user of aterminal device is a person with the legitimate right to use theterminal device for thereby protecting the terminal device againstunauthorized use by a third party, the terminal lock system comprising akey device and a terminal-associated device. The key device is portableand has a radio communication means for performing short-range wirelesscommunications. The terminal-associated device requests a connection tothe key device through the short-range wireless communications, andinhibits the terminal device which is combined with theterminal-associated device from being used if information of the keydevice which is confirmed as being connected to the terminal-associateddevice does not agree with information registered in theterminal-associated device, or if the terminal-associated device is notconfirmed as being connected to the key device through the short-rangewireless communications.”

SUMMARY OF THE INVENTION

In JP-A-2004-102682, the following advantage will be described. “Withthe above arrangement, when the user who is carrying the key devicemoves away from the terminal device combined with theterminal-associated device until the terminal-associated device and thekey device are no longer capable of connecting to each other based on ashort-range wireless communication technique, the terminal-associateddevice locks the terminal device against use. The terminal lock systemthus authenticates the user without the need for asking the user to makeany action, and reliably protects the terminal device againstunauthorized use by a third party.”

However, the user needs to always carry the dedicated key device havinga communication function when using the terminal device.

In view of the foregoing, it is an object of the present invention toprovide a convenient mobile terminal and control method thereof capableof being protected against unauthorized use by a third party withoutusing the dedicated key device.

The object of the present invention can be attained by the followingtechnical proposal: For example, a plurality of mobile terminals arepreviously registered mutually. When unlocked among them, one mobileterminal communicates with another mobile terminal in a communicationrange of the short-range wireless communications, unlocks the aboveanother mobile terminal, and when out of the communication range, locksit again.

According to the present invention, for example, when one mobileterminal is unlocked among a plurality of mobile terminals, anothermobile terminal can be unlocked.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of a mobileterminal according to a first embodiment;

FIG. 2 is a flowchart illustrating operations for locking and releasinga mobile terminal 1 according to a first embodiment;

FIG. 3 is a flowchart illustrating operations for locking and releasinga mobile terminal 2 according to a first embodiment;

FIG. 4 is a flowchart illustrating operations for locking and releasinga mobile terminal 1 according to a second embodiment;

FIG. 5 is a flowchart illustrating operations for locking and releasinga mobile terminal 2 according to a second embodiment;

FIG. 6 is a flowchart illustrating operations for locking and releasinga mobile terminal 1 according to a third embodiment;

FIG. 7 is a display example illustrating a liquid crystal panel of amobile terminal according to a third embodiment;

FIG. 8 is a flowchart illustrating operations for locking and releasinga mobile terminal 1 according to a fourth embodiment;

FIG. 9 is a flowchart illustrating operations for locking and releasinga mobile terminal 1 according to a fifth embodiment; and

FIG. 10 is a flowchart illustrating a warning operation of a mobileterminal 1 according to a sixth embodiment.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings of theembodiments.

First Embodiment

FIG. 1 is a block diagram illustrating a configuration of a mobileterminal according to a first embodiment of the present invention. Themobile terminals 1 and 2 each have a radio communication function, andtransmit and receive a variety of information to and from a mobile basestation 3. Further, the mobile terminals 1 and 2 each have a function ofperforming short-range wireless communication between mobile terminals,and can transmit and receive a variety of information between the mobileterminals 1 and 2 by using the function. Examples of the short-rangewireless communication include Bluetooth (trademark), infrared rays, andWi-Fi Direct.

A controller 11 controls each unit of the mobile terminal 1. Thecontroller 11 is configured by a CPU (Central Processing Unit), anarbitrary control circuit, or a dedicated circuit such as an ASIC.

A display unit 12 of the mobile terminal 1 is configured, for example,by a liquid crystal panel, and displays a variety of information. Anoperating unit 13 is configured, for example, by a push-button switch ora touch panel, and an instruction of a user is transferred to thecontroller 11. A wireless communications unit 15 and a short-rangewireless communication unit 16 are each configured by a communicationcircuit including an encoding circuit and a decoding circuit in additionto an antenna. The wireless communications unit 15 communicates with themobile base station 3. The short-range wireless communication unit 16controls short-range wireless communications and communicates, forexample, with the mobile terminal 2.

A storage unit 14 stores a program or various kinds of settinginformation for controlling a mobile terminal, and a password forunlocking a mobile terminal.

A controller 21, a display unit 22, an operating unit 23, a storage unit24, and a wireless communications unit 25 of the mobile terminal 2 arethe same as the controller 11, the display unit 12, the operating unit13, the storage unit 14, and the wireless communications unit 15 of themobile terminal 1, and therefore, descriptions will not be repeatedhere. A short-range wireless communication unit 26 controls short-rangewireless communications, and communicates, for example, with the mobileterminal 1.

Next, descriptions will be made about operations which are set until themobile terminal 2 is unlocked after the mobile terminal 1 is unlocked.

In addition, the locked state of the present embodiment is a state inwhich functions or operations of part or the whole of a mobile terminalare limited.

When the user refers to the display unit 12 of the mobile terminal 1 andoperates the operating unit 13 so as to release a locked state, themobile terminal 1 searches whether another mobile terminal is in ashort-distance communication range capable of performing short-rangewireless communications. The mobile terminal 1 further confirms whetherit is the mobile terminal 2 being a previously registered mobileterminal. When the mobile terminal 1 confirms that information stored inthe storage unit 14 is matched with that of the storage unit 24 and itis the previously registered mobile terminal, the mobile terminal 2 isunlocked.

The mobile terminals 1 and 2 are supposed to transit to a locked statewhen not operated for a given length of time and, for example, apassword is supposed to need to be entered in order to release thelocked state. The given length of time is, for example, thirty seconds.Further, the mobile terminals 1 and 2 are previously registered so as tobe mutually locked and unlocked through short-range wirelesscommunications.

An example where the mobile terminals 1 and 2 each have a radiocommunication function with the mobile base station 3 is illustrated.Further, the mobile terminal 1 and/or mobile terminal 2 may each have awireless LAN (Local Area Network) function, and transmit and receive avariety of information to and from a wireless LAN router.

FIG. 2 is a flowchart illustrating operations of locking and unlockingthe mobile terminal 1 according to the first embodiment.

First, at step S201, the mobile terminal 1 confirms whether to beunlocked when the user enters a password. The mobile terminal 1continues to wait for unlocking until the locked state is released, andwhen it is unlocked, the process proceeds to step S202. An example wherethe user enters a password is described here, and biometricsauthentication may be further used.

At step S202, the mobile terminal 1 searches mobile terminals in theneighborhood through short-range wireless communications. For example,the mobile terminal 1 transmits radio waves used for the short-rangewireless communications and searches for a mobile terminal in which theshort-range wireless communications are established by receiving theradio waves.

At step S203, the mobile terminal 1 determines whether there is a mobileterminal in the neighborhood and it is the previously registered mobileterminal, and switches the process. If so, the process advances to stepS204. If not, the process proceeds to step S205.

At step S204, the mobile terminal 1 unlocks the previously registeredmobile terminal 2 through the short-range wireless communications. Forexample, the mobile terminal 1 transmits a signal for instructing themobile terminal 2 to be unlocked thereto. Here, the mobile terminals 1and 2 are supposed to be previously registered mutually by the sameuser.

At step S205, the mobile terminal 1 confirms whether to be instructed tobe locked by the user. If so, the process proceeds to step S207. At stepS206, the mobile terminal 1 further confirms whether not to be operatedfor a given length of time. If not, the process proceeds to step S207.If so, the process returns to step S205.

At step S207, the mobile terminal 1 locks the previously registeredmobile terminal 2 through the short-range wireless communications. Forexample, the mobile terminal 1 transmits a signal for instructing themobile terminal 2 to be locked thereto.

At step S208, the mobile terminal 1 is locked.

FIG. 3 is a flowchart illustrating operations for locking and unlockingthe mobile terminal 2 according to the first embodiment.

First, at step S301, the mobile terminal 2 confirms whether to beunlocked when the user enters a password. If so, the process proceeds tostep S303. At step S302, the mobile terminal 2 further confirms whetherto be unlocked through the short-range wireless communications. If so,the process proceeds to step S305. If not, the process returns to stepS301.

At step S303, the mobile terminal 2 confirms whether to be instructed tobe locked by the user. If so, the process proceeds to step S307. At stepS304, the mobile terminal 2 further confirms whether not to be operatedfor a given length of time. If not, the process proceeds to step S307.If so, the process returns to step S303.

At step S305, the mobile terminal 2 confirms whether to be out of thecommunication range of the short-range wireless communications with themobile terminal 1. If so, the process proceeds to step S307. At stepS306, the mobile terminal 2 further confirms whether to be instructed tobe locked by the mobile terminal 1 through the short-range wirelesscommunications. If so, the process proceeds to step S307. If not, theprocess returns to step S305.

At step S307, the mobile terminal 2 is locked.

In addition, the mobile terminal 1 may detect that the short-rangewireless communications established with the mobile terminal 2 isbroken, and transmit a signal for instructing the mobile terminal 2 tobe locked thereto immediately before the communication is broken.

In the first embodiment of the present invention, a plurality of mobileterminals are previously registered mutually through the aboveconfiguration. When one mobile terminal is unlocked among them, anothermobile terminal is unlocked in the communication range of theshort-range wireless communications. When out of the communicationrange, the another mobile terminal can be locked again.

In the present embodiment, an example where two mobile terminals arelocked and unlocked is described; similarly, three or more mobileterminals can be further locked and unlocked.

Second Embodiment

FIG. 4 is a flowchart illustrating operations for locking and unlockingthe mobile terminal 1 according to a second embodiment of the presentinvention. The mobile terminal has the same configuration as that of thefirst embodiment, and therefore descriptions will not be repeated here.

First, at step S401, the mobile terminal 1 confirms whether to beunlocked when the user enters a password. If so, the process proceeds tostep S403. At step S402, the mobile terminal 1 further confirms whetherto be unlocked through the short-range wireless communications. If so,the process proceeds to step S409.

Steps S403 to S408 are the same as steps S202 to S207 of FIG. 2, andtherefore descriptions will not be repeated here.

At step S409, the mobile terminal 1 confirms whether to be out of thecommunication range of the short-range wireless communications with themobile terminal 2. If so, the process proceeds to step S411. At stepS410, the mobile terminal 1 further confirms whether to be instructed tobe locked through the short-range wireless communications. If so, theprocess proceeds to step S411. If not, the process returns to step S409.

At step S411, the mobile terminal 1 is locked.

FIG. 5 is a flowchart illustrating operations for locking and unlockingthe mobile terminal 2 according to the second embodiment.

First, at step S501, the mobile terminal 2 confirms whether to beunlocked when the user enters a password. If so, the process proceeds tostep S503. At step S502, the mobile terminal 2 further confirms whetherto be unlocked through the short-range wireless communications. If so,the process proceeds to step S509.

Steps S503 and S504 are the same as steps S403 and S404 of FIG. 4, andtherefore descriptions will not be repeated here.

At step S505, the mobile terminal 2 unlocks the previously registeredmobile terminal 1 through the short-range wireless communications.

At step S506, the mobile terminal 2 confirms whether to be instructed tobe locked by the user. If so, the process proceeds to step S508. At stepS507, the mobile terminal 2 further confirms whether not to be operatedfor a given length of time. If not, the process proceeds to step S508.

At step S508, the mobile terminal 2 locks the previously registeredmobile terminal 1 through the short-range wireless communications.

At step S509, the mobile terminal 2 confirms whether to be out of thecommunication range of the short-range wireless communications with themobile terminal 1. If so, the process proceeds to step S511. At stepS510, the mobile terminal 2 further confirms whether to be instructed tobe locked through the short-range wireless communications. If so, theprocess proceeds to step S511. If not, the process returns to step S509.

At step S511, the mobile terminal 2 is locked.

In the second embodiment of the present invention, a plurality of mobileterminals are previously registered mutually through the aboveconfiguration. When one mobile terminal is unlocked among them, anothermobile terminal is unlocked in the communication range of theshort-range wireless communications. When out of the communicationrange, the another mobile terminal can be locked again.

First, any mobile terminal may be unlocked. Even if any mobile terminalis unlocked, another mobile terminal can be unlocked, and therefore themobile terminal of the second embodiment is more convenient than that ofthe first embodiment.

In the present embodiment, an example where two mobile terminals arelocked and unlocked is described; similarly, three or more mobileterminals can be further locked and unlocked.

Third Embodiment

FIG. 6 is a flowchart illustrating operations for locking and unlockingthe mobile terminal 1 according to a third embodiment of the presentinvention. The mobile terminal has the same configuration as that of thefirst embodiment, and therefore descriptions will not be repeated here.

Steps S601 to S604 are the same as steps S401 to S404 of FIG. 4, andtherefore descriptions will not be repeated here.

At step S605, the mobile terminal 1 displays a confirmation screen inwhich the mobile terminal 2 is unlocked. A display example will bedescribed later.

At step S606, the mobile terminal 1 confirms whether the user instructsthe mobile terminal 2 to be unlocked. If so, the process advances tostep S607. If not, the process proceeds to step S608.

Steps S608 to S613 are the same as steps S406 to S411 of FIG. 4, andtherefore descriptions will not be repeated here.

FIG. 7 is a display example illustrating a liquid crystal panel of themobile terminal 1 at the time of detecting the mobile terminal 2 throughthe short-range wireless communications at step S605 of FIG. 6. Adetection report of the mobile terminal 2, a selection button, andnon-selection button of the unlocking are displayed on the liquidcrystal panel. When detecting the mobile terminal 2 through theshort-range wireless communications, the mobile terminal 1 transits toan unlocking selection mode. On the liquid crystal panel 73, anunlocking selection button 74 and an unlocking non-selection button 76are displayed. When the user pushes a push-button switch 75corresponding to the unlocking selection button 74, the mobile terminal2 is unlocked. When the user pushes a push-button switch 77corresponding to the unlocking non-selection button 76, the mobileterminal 1 releases the unlocking selection mode and returns to a normalmode.

In the third embodiment of the present invention, a plurality of mobileterminals are previously registered mutually through the aboveconfiguration. When one mobile terminal is unlocked among them, anothermobile terminal is unlocked in the communication range of theshort-range wireless communications. When out of the communicationrange, the another mobile terminal can be locked again.

Further, upon detection of another mobile terminal, the user can selectwhether to unlock it.

Fourth Embodiment

FIG. 8 is a flowchart illustrating operations for locking and unlockingthe mobile terminal 1 according to a fourth embodiment of the presentinvention. The mobile terminal has the same configuration as that of thefirst embodiment, and therefore descriptions will not be repeated here.

First, at step S801, the mobile terminal 1 searches mobile terminals inthe neighborhood through the short-range wireless communications.

At step S802, the mobile terminal 1 determines whether there is a mobileterminal in the neighborhood and it is the previously registered mobileterminal, and switches the process. If so, the process advances to stepS803. If not, the process proceeds to step S805.

At step S803, the mobile terminal 1 requests the user to enter a simplepassword, and continues to wait until it is correctly entered at stepS804. When the simple password is entered, the process proceeds to stepS807.

At step S805, the mobile terminal 1 requests the user to enter acomplicated password, and continues to wait until it is correctlyentered at step S806. When the complicated password is entered, theprocess proceeds to step S807.

The simple password is, for example, a three-character number, and thecomplicated password is, for example, a ten-character number. That is,strengths of both passwords are different from each other.

At step S807, the mobile terminal 1 is unlocked. Here, the mobileterminals 1 and 2 are supposed to be previously registered mutually bythe same user.

At step S808, the mobile terminal 1 confirms whether to be instructed tobe locked by the user. If so, the process proceeds to step S810. At stepS809, the mobile terminal 1 further confirms whether not to be operatedfor a given length of time. If not, the process proceeds to step S810.

At step S810, the mobile terminal 1 is locked.

Operations for locking and unlocking the mobile terminal 2 are the sameas those of the mobile terminal 1.

In the fourth embodiment of the present invention, a plurality of mobileterminals are previously registered mutually through the aboveconfiguration. When both mobile terminals are in the communication rangeof the short-range wireless communications, an authentication level forunlocking the mobile terminal is simplified. When both the mobileterminals are out of the communication range of the short-range wirelesscommunications, an authentication level for unlocking the mobileterminal is detailed. Therefore, as compared to a case of simply fixingthe authentication level, safety is high. On the other hand, as comparedto a case of fixing the authentication level in detail, usability ispreferable.

In the present embodiment, an example where the number of characters ofthe password is changed is described as switching of the authenticationlevel. Further, there may be changed a principal matching rate ofbiometrics authentication such as face and finger authentication types,or a character matching rate of character authentication.

In the present embodiment, an example where two mobile terminals arelocked and unlocked is described; similarly, three or more mobileterminals can be further locked and unlocked.

Fifth Embodiment

FIG. 9 is a flowchart illustrating operations for locking and unlockingthe mobile terminal 1 according to a fifth embodiment of the presentinvention. The mobile terminal has the same configuration as that of thefirst embodiment, and therefore descriptions will not be repeated here.

First, at step S901, the mobile terminal 1 searches mobile terminals inthe neighborhood through the short-range wireless communications.

At step S902, the mobile terminal 1 determines whether there is a mobileterminal in the neighborhood and it is the previously registered mobileterminal, and switches the process. If so, the process proceeds to stepS903. If not, the process returns to step S901.

At step S903, the mobile terminal 1 is unlocked. Here, the mobileterminals 1 and 2 are supposed to be previously registered mutually bythe same user.

At step S904, the mobile terminal 1 confirms whether to be out of thecommunication range of the short-range wireless communications with themobile terminal 2. The mobile terminal 1 continues to wait until out ofthe communication range. When the mobile terminal 1 is out of thecommunication range, the process proceeds to step S905.

At step S905, the mobile terminal 1 is locked.

Operations for locking and unlocking the mobile terminal 2 are the sameas those of the mobile terminal 1.

In the fifth embodiment of the present invention, a plurality of mobileterminals are previously registered mutually through the aboveconfiguration. When in the communication range of the short-rangewireless communications, they are mutually unlocked. When out of thecommunication range, they are locked again. Therefore, the mobileterminal of the present embodiment is more convenient than those of thefirst and second embodiments.

In the present embodiment, an example where two mobile terminals arelocked and unlocked is described; similarly, three or more mobileterminals can be further locked and unlocked.

Sixth Embodiment

FIG. 10 is a flowchart illustrating a warning operation of the mobileterminal 1 according to a sixth embodiment of the present invention. Themobile terminal has the same configuration as that of the firstembodiment, and therefore descriptions will not be repeated here.

First, at step S1001, the mobile terminal 1 searches mobile terminals inthe neighborhood through the short-range wireless communications.

At step S1002, the mobile terminal 1 determines whether there is amobile terminal in the neighborhood and it is the previously registeredmobile terminal, and switches the process. If so, the process proceedsto step S1003. If not, the process returns to step S1001.

At step S1003, the mobile terminal 1 confirms whether to be out of thecommunication range of the short-range wireless communications with themobile terminal 2. If so, the process proceeds to step S1004. If not,the process returns to step S1003.

At step S1004, the mobile terminal 1 gives warning to the user throughsounds or vibrations. Alternatively, the mobile terminal 1 sends a mailto another mobile terminal. At this time, when having a GPS (GlobalPosition System) function, the mobile terminal 1 may transmit positionalinformation to the another mobile terminal.

The warning operation of the mobile terminal 2 is the same as that ofthe mobile terminal 1.

In the sixth embodiment of the present invention, a plurality of mobileterminals are previously registered mutually through the aboveconfiguration. In the case where they are once in the communicationrange of the short-range wireless communications, upon being out of thecommunication range next, the mobile terminal 1 notifies the user ofthat effect, thereby preventing the mobile terminals from being lost.

Suppose, for example, that the present embodiment is combined with thefirst embodiment. In this case, the mobile terminal 2 can notify theuser that the mobile terminal 2 is locked because of moving to theoutside of the communication range of the short-range wirelesscommunications with the mobile terminal 1.

In the present embodiment, an example where two mobile terminals performa warning operation is described; similarly, three or more mobileterminals can further perform a warning operation.

In addition, the above-described embodiments are described in detail inorder to clearly describe the present invention, and are not necessarilylimited to the mobile terminal having all the described constructions.Further, a part of configurations according to one embodiment can bereplaced by those according to other embodiments, and the configurationsaccording to other embodiments can be added to that according to oneembodiment. Further, an addition, deletion, or replacement of theconfigurations according to other embodiments can be performed by usinga part of the configurations according to each embodiment.

A part or all of the respective structures, functions, processing units,and processing approaches may be realized by hardware by designingthrough the integrated circuit, for example. Those structures, functionsand the like may be realized by software by interpreting and executingthe program for realizing the respective functions through a processor.Information with respect to the program, table, and file for realizingthe respective functions may be stored in the recording unit such as thememory, hard disk, and SSD (Solid State Drive), or the recording mediumsuch as the IC card and SD card.

The examples show the control line and information line considered asnecessary for the explanation, which does not necessarily show all thecontrol lines and information lines of the product. Actually, almost allthe components may be considered to be connected with one another.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. A mobile terminal to transit to a locked state in which apredetermined operation is limited, comprising: a communication unitwhich performs short-range wireless communications; storage unit whichpreviously stores information about another mobile terminal; and a lockcontrol instruction unit which communicates with the another mobileterminal in a communication range through the communication unit andinstructs the another mobile terminal to be unlocked when releasing alocked state based on an operation of a user.
 2. The mobile terminalaccording to claim 1, wherein: when transiting to a locked state basedon an operation of a user, the lock control instruction unitcommunicates with the another mobile terminal in a communication rangethrough the communication unit and instructs the another mobile terminalto transit to a locked state.
 3. The mobile terminal according to claim1, wherein: out of a communication range with the another mobileterminal, the mobile terminal transits to a locked state.
 4. The mobileterminal according to claim 1, wherein: before unlocking the anothermobile terminal, the mobile terminal requests confirmation from a user.5. A mobile terminal to transit to a locked state in which apredetermined operation is limited, comprising: a communication unitwhich performs short-range wireless communications; a storage unit whichpreviously stores information about another mobile terminal; and anauthentication unit which performs authentication to release the lockedstate, wherein the authentication unit requests relatively simpleauthentication when capable of communicating with the another mobileterminal through the communication unit, and requests relativelycomplicated authentication when incapable of communicating with theanother mobile terminal.
 6. A mobile terminal to transit to a lockedstate in which a predetermined operation is limited, comprising: acommunication unit which performs short-range wireless communications; astorage unit which previously stores information about another mobileterminal; and a lock control instruction unit which communicates withthe another mobile terminal in a communication range through thecommunication unit, instructs the another mobile terminal to beunlocked, and instructs the another mobile terminal to transit to alocked state when out of the communication range.
 7. A mobile terminalcomprising: a communication unit which performs short-range wirelesscommunications; a storage unit which previously stores information aboutanother mobile terminal; and a warning unit which communicates with theanother mobile terminal in a communication range through thecommunication unit, and when the another mobile terminal is out of thecommunication range, notifies a user of that effect.
 8. A method forcontrolling a mobile terminal to transit to a locked state in which apredetermined operation is limited, comprising the steps of: performingshort-range wireless communications; storing information about anothermobile terminal; and communicating with the another mobile terminal in acommunication range of the short-range wireless communications andinstructing the another mobile terminal to be unlocked when releasing alocked state based on an operation of a user.
 9. A method forcontrolling a mobile terminal to transit to a locked state in which apredetermined operation is limited, comprising the steps of: performingshort-range wireless communications; storing information about anothermobile terminal; and requesting relatively simple authentication whencapable of performing short-range wireless communications with theanother mobile terminal and requesting relatively complicatedauthentication when incapable of performing short-range wirelesscommunications with the another mobile terminal upon releasing thelocked state.
 10. A method for controlling a mobile terminal to transitto a locked state in which a predetermined operation is limited,comprising the steps of: performing short-range wireless communications;storing information about another mobile terminal; and communicatingwith the another mobile terminal in a communication range of theshort-range wireless communications, instructing the another mobileterminal to be unlocked, and instructing the another mobile terminal totransit to a locked state when out of the communication range.
 11. Amethod for controlling a mobile terminal, comprising the steps of:performing short-range wireless communications; storing informationabout another mobile terminal; and communicating with the another mobileterminal in a communication range of the short-range wirelesscommunications, and when the another mobile terminal is out of thecommunication range, notifying a user of that effect.